1. Field of the Invention
The present invention relates to a high-pressure fuel-feed pump which is used in an engine.
2. Discussions of Background
In FIG. 6, there is shown a sectional view of a conventional high-pressure fuel-feed pump. In this Figure, reference numeral 1 designates the high-pressure fuel feed pump which can be mounted to e.g. a housing of an engine (not shown), reference numeral 2 designates an intake port of the pump, reference numeral 3 designates an intake passage which forms the intake port, reference numeral 4 designates an intake valve which is arranged in an intake passage for fuel entering from the intake passage, reference numeral 5 designates a valve seat which has the intake valve contacted therewith and separated therefrom, reference numeral 6 designates a compression coil spring which urges the intake valve 4 against the valve seat 5, reference numeral 7 designates a spring guide which guides the compression coil spring, reference numeral 8 designates a threaded portion, reference numeral 9 designates a copper washer.
Reference numeral 10 designates a delivery valve as a locking member, reference numeral 11 designates a discharge valve which forms the delivery valve, reference numeral 12 designates a valve seat which has the discharge valve contacted therewith and separated therefrom, reference numeral 13 designates a compression coil spring which urges the discharge valve which against the valve seat 12, reference numeral 14 designates a discharge port, reference numeral 15 designates a threaded portion which is formed on outer periphery of a lower portion of the delivery valve 10, reference numeral 16 designates a seal housing portion which is formed on the outer periphery of the delivery valve at a position higher than the threaded portion, reference numeral 17 designates a pump body which has the delivery valve 10, the intake valve 4 and other members mounted thereto, reference numeral 18 designates a threaded portion which is formed in the pump body to have the intake port 2, the intake valve 4 and other members screwed therein, and reference numeral 19 designates a threaded potion which is formed on the pump body 17 to have the delivery valve 10 mounted thereto.
Reference numeral 20 designates a cylinder which is arranged between the delivery valve 10 and the pump body 17. Reference numeral 21 designates an annular fixing portion which is formed on an upper portion of the cylinder, and which receives a compression force in a longitudinal direction (a vertical direction) when the delivery valve 10 is screwed into the pump body 17.
Reference numeral 22 designates a cylindrical sliding portion of the cylinder which is integrally continuous to the fixing portion and extends in the longitudinal direction, reference numeral 23 designates a plunger which is reciprocated in the sliding portion of the cylinder, and reference numeral 24 designates a tappet which receives a head portion 23a on a lower end of the plunger, which is formed in a bottomed shape, and which is supported in a tappet sliding portion 17a of the pump body 17 so as to be slidable. Reference numeral 25 designates a spring seat which is mounted to the lower end of the plunger 23. Reference numeral 26 designates a compression coil spring which is arranged between the spring seat and the pump body 17, and which urges the spring seat 25 and the plunger 23 downwardly.
Reference numeral 27 designates a cam which contacts with the tappet 24, and which is driven by the engine at a half of the rotation of the engine. Reference numeral 28 designates a fuel pressurization chamber which is defined by the cylinder 20 and the plunger 23, reference numeral 29 designates a copper washer which is arranged between the pump body 17 and the cylinder 20. Reference numeral 30 designates an O ring which is arranged in the seal housing portion 16 of the delivery valve 10. Reference numeral 31 designates a copper washer which is arranged between the delivery valve 10 and the cylinder 20.
When the unshown engine starts and rotates the cam 27, the plunger 23 is reciprocated through the tappet 24.
When the plunger slides downwardly, the intake valve 4 lifts against the action of the compression coil spring 6, allowing fuel to be inspired into the fuel pressurization chamber 28 through the intake passage 3.
When the plunger 23 slides upwardly, the discharge valve 11 is urged by the compression coil spring 13 to contact with the valve seat 12 until the pressure in the fuel pressurization chamber 28 reaches a predetermined value. When the pressure in the fuel pressurization chamber 28 reaches the predetermined value by a further raise of the plunger 23, the discharge valve 11 lifts upwardly to open against the action of the compression coil spring 13, the fuel is supplied to a fuel pipe at a high pressure side (not shown) through the discharge port 14.
When such a conventional device is assembled, the cylinder 20 is inserted into a hollow accommodation portion of the pump body 17 through the copper washer 29, the delivery valve 10 with the discharge valve 11 and the compression coil spring 13 housed therein is screwed into the pump body 17 through the copper washer 31 on the cylinder 20 by engaging the threaded portions 19 and 15, and the delivery valve 10 is downwardly screwed to be tightened. At that time, the fixing portion 21 of the cylinder 20 receives the compression force in the longitudinal direction by the screwing of the delivery valve 10 to be firmly sandwiched between the delivery valve 10 and the pump body 17.
On the other hand, the intake port 2 with the intake valve 4, the valve seat 5, the compression coil spring 6 and the spring guide 7 housed therein is screwed in a hollow accommodation portion in a right side of the pump 17 through the treaded portion 8.
Next, the plunger 23 is inserted into the sliding portion 22 of the cylinder 20 from below the pump body 17 through the compression coil spring 26 and the spring seat 25, and the tappet 24 is mounted in the tappet sliding portion 17a of the pump body 17 so as to be slidable therein so that the tappet supports the plunger head portion 23a.
In the conventional high-pressure fuel-feed pump, when the delivery valve 10 as the locking member is screwed into the pump body 17, the fixing portion 21 of the cylinder 20 is subjected to the compression force in the longitudinal direction by the screwing of the delivery valve 10. The conventional fuel-feed pump has involved a problem in that, as shown in FIG. 7, the compression force deforms an inner peripheral surface of the sliding portion 22 to provide inward projection so as to contact the inner peripheral surface with the plunger 23, causing the plunger 23 to be abnormally worn and be subjected to seizing.
A raise in the discharge pressure of the high-pressure fuel-feed pump deteriorates sealing property between the delivery valve 10 and the cylinder 20, and between the pump body 17 and the cylinder 20, providing need for an increase in a tightening force of the locking member such as the delivery valve 20. This has created a problem in that the deformation of the inner periphery surface of the sliding portion 22 is further developed to subject the plunger 23 to easy seizing.